Derailleur of a bicycle gearshift and method for electronically controlling a bicycle gearshift

ABSTRACT

A method for electronically controlling a bicycle gearshift comprising a support unit configured to be mounted on a bicycle frame at an assembly of toothed wheels coaxial with one another of the gearshift and a mobile unit comprising a chain guide. The method comprising the steps of:
         moving the mobile unit to impart on the chain guide a primary displacement having at least a component in axial direction with respect to an axis (Z) of the assembly of toothed wheels; and,   moving the mobile unit to impart onto the chain guide a secondary displacement having at least a component in radial direction with respect to the axis (Z) of the assembly of toothed wheels, wherein the secondary displacement is carried out independently of the primary displacement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Italian Application No.MI2014A002070, which was filed on Dec. 2, 2014 and is incorporatedherein by reference as if fully set forth.

FIELD OF INVENTION

The present invention relates to a derailleur of a bicycle gearshift,preferably an electronically servo-assisted bicycle gearshift, as wellas to a method for electronically controlling a bicycle gearshift.

BACKGROUND

A motion transmission system in a bicycle comprises a chain extendingbetween toothed wheels associated with the axle of the pedal cranks andwith the hub of the rear wheel. When there is an assembly of toothedwheels comprising more than one toothed wheel at at least one of theaxle of the pedal cranks and the hub of the rear wheel, and the motiontransmission system is therefore provided with a gearshift, a frontderailleur and/or a rear derailleur are provided for. Inhigh-performance bicycles, and particularly in bicycles used in sportscompetitions, characteristics that are very important to the cyclist arethe speed and precision with which gearshifting can be performed.Particularly for this reason, so-called electronic gearshifts, or morespecifically electronically servo-assisted gearshifts, have becomecommon.

In case of an electronically servo-assisted gearshift, each derailleurcomprises a guide element—also known as chain guide or cage or, in caseof a rear derailleur, rocker arm—movable to displace the chain among thetoothed wheels in order to change the gear ratio, and anelectromechanical actuator to displace the chain guide. The actuator inturn typically comprises a motor, typically an electric motor, coupledwith the chain guide through a linkage such as an articulatedparallelogram, a rack system or a worm screw system, as well as a sensoror transducer of the position, speed, acceleration and/or direction ofrotation of the rotor or of any moving part downstream of the rotor,down to the chain guide itself. It is worthwhile noting that slightlydifferent terminology from that used in this context is also in use.

Control electronics changes the gear ratio automatically, for examplebased on one or more detected variables, such as the travel speed, thecadence of rotation of the pedal cranks, the torque applied to the pedalcranks, the slope of the travel terrain, the heart rate of the cyclistand similar, and/or the gear ratio is changed based on commands manuallyinput by the cyclist through suitable control members, for examplelevers and/or buttons.

A device or unit for controlling the front derailleur and a device orunit for controlling the rear derailleur—or only one of the two in caseof simpler gearshifts—are mounted so as to be easily manoeuvred by thecyclist, normally on the handlebars, close to the handgrips thereofwhere the brake lever is also located for controlling the brake of thefront and rear wheel, respectively. Control devices that allow to driveboth a derailleur in the two directions and a brake are commonly calledintegrated controls.

It is in general known to drive the derailleur of a bicycle gearshiftwith reference to values of a table of command values, each correlatedto a position of the derailleur in which engagement of the chain with aspecific toothed wheel occurs or there is. In other words, the controlelectronics or controller uses the table of command values to obtain thevalue that a variable of the derailleur must take to position the chainin engagement with the desired toothed wheel. Such a value can be adifferential value with respect to the adjacent toothed wheel, or it canbe an absolute value with respect to a reference, for example withrespect to a reference toothed wheel or to an end of stroke condition ora condition of lack of excitation of the motor.

From the point of view of magnitude, an actuator command value of thetable of values can be, for example, the distance travelled by a mobilepoint taken as a reference on the derailleur, the number of steps orrevolutions that the motor should be made to perform, a length ofexcitation time of the motor, the value of a supply voltage of a motorhaving an excursion proportional to the voltage, or furthermore it canbe the value emitted by the sensor or transducer associated with themotor, a numerical value stored in a register and representative of oneof the aforementioned quantities, etc.

In particular, the motors of actuators can be driven for a number ofsteps or for a length of excitation time or with a voltage that areappropriate for each upward or downward gearshifting and then stoppedautomatically, while the sensors are used to provide a feedback signalto the control electronics so that it can possibly take care ofactuating the motors of the actuators again in case the intendedposition has not been reached, namely in case the aforementionedvariable of the derailleur has not taken the table value. This may, forexample, be due to the fact that the resistance torque offered by thederailleur, which is to a certain extent dependent on how the cyclist ispedalling, was too high, greater than the maximum torque able to bedelivered by the motors through the linkage.

The values of said table of command values are nominal values, set inthe factory, which take the number of toothed wheels in the derailleur(front or rear) and the respective thicknesses and pitches into account.Typically, such nominal values provide that, in the absence of theactuator driving signal, namely with command value at zero, the chain isin engagement with the toothed wheel having the smallest diameter,although, as can be seen from the aforementioned examples, thiscondition is not necessary.

Although with electronically servo-assisted gearshifts it has beenpossible to improve precision and speed of gearshifting, there is stilla need to improve these performances, in order to be able to assist thecyclist in achieving better and better results in competition andprotect the mechanics.

This requirement is clearly of increasing importance the more thegearshift is intended to be used in high-level cycling competitions.

In order to obtain high precision of control of known bicyclegearshifts, an initial adjustment of the bicycle is carried out in orderto optimize the tensioning of the chain depending on the configurationand structure of the frame and the assembly of toothed wheels, both thefront ones (crowns) associated with the axle of the pedal cranks, andthe rear ones (sprockets) associated with the rear wheel.

It is possible to adapt the command values of the table so that theyaccurately correspond to the electromechanical components of thespecific gearshift, in particular to the pitches of the toothed wheelsand/or to the mutual position of the elements of the motor or of thelinkage taken as fixed reference and as mobile reference, as well aspossibly to the progress of the actuation voltage of the motor, to thespeed, acceleration and/or direction of rotation of the motor, etc.

Moreover, the initial adjustment typically acts on at least one springprovided for in the transmission, possibly setting a preload on it, inorder to keep the correct tension of the transmission chain in thedifferent travel configurations.

In some gearshifts, used particularly for road bicycles, there are twochain tensioning springs counteracting to determine the setup of thechain guide when engaged with the transmission chain. This allowsgreater versatility of the system, providing it with high elasticity.Other gearshifts, on the other hand, can provide for only one chaintensioning spring.

PRIOR ART

According to the prior art, the initial preload setting of the chaintensioning spring(s) is so carried out as to bring the chain guideradially as close as possible to the toothed wheels.

Indeed, a short distance between the chain guide and the toothed wheelsdetermines greater sensitivity of control since, in such conditions, thechain guide displacement component parallel to the axis of the toothedwheels corresponds to a slope exerted on the chain that is sufficient totrigger a displacement from one toothed wheel to the other.

Bringing the chain guide closer to the toothed wheels does, however,have a limitation dictated by the toothed wheel of maximum diameter.Indeed, bringing it too close to the toothed wheel of maximum diameteris the cause of drawbacks such as the feeling of a rough gearshiftbetween the gear ratio that uses such a toothed wheel and the next one,as well as scraping between the chain and the chain guide in case thechain is engaged with the toothed wheel of maximum diameter whilepedalling backwards. In such conditions, the transmission can also beannoyingly noisy.

In order to improve the precision of gearshifting, the Applicantrecently proposed, in the patent application published as US2014/0243129, to provide for the preload of the chain tensioning springto be adjusted as a function of the primary displacement of the chainguide in the direction of the axis of the assembly of toothed wheels,and in particular for it to be a mechanical consequence of the primarydisplacement of the chain guide. In this way, the radial distance of thechain guide from the axis of the assembly of toothed wheels changesdepending on which toothed wheel is engaged with the chain; inparticular, the distance from the axis will be increasingly greater asthe diameter of the toothed wheel engaged by the chain increases.

The problem at the basis of the present invention is to further improveprecision and speed of gearshifting in a derailleur of a bicyclegearshift.

SUMMARY OF THE INVENTION

The invention provides a bicycle gearshift derailleur with a mobilechain guide that has actuators for both primary and secondarydisplacements. The primary displacement of the mobile chain guide has acomponent in an axial direction with respect to an axis of an assemblyof toothed wheels. The secondary displacement of the mobile chain guidehas a component in a radial direction with respect to the axis of anassembly of toothed wheels. The second actuator can move the mobilechain guide independently of the primary actuator.

The secondary displacement independent of the primary displacement makesit is possible to ensure that the mobile unit—and in particular thechain guide—is always in the ideal position with respect to the assemblyof toothed wheels. Typically, during gearshifting it will be in aposition relatively radially close to the toothed wheels, while duringnormal travel it will be in a position relatively radially far.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will become clearerfrom the following detailed description of some preferred embodimentsthereof, made with reference to the attached drawings. The differentfeatures in the single configurations can be combined as desired. Insuch drawings,

FIG. 1 schematically shows the present invention,

FIG. 2 is a block diagram relating to a first gearshifting modeaccording to the invention,

FIGS. 3-7 are diagrammatic views of a sequence of positions of thederailleur during upward gearshifting carried out with such a mode,

FIGS. 8-12 are diagrammatic views of a sequence of positions of thederailleur during downward gearshifting carried out with such a mode,

FIGS. 13 and 14 are block diagrams relating to other gearshifting modesaccording to the invention,

FIG. 15 is a block diagram relating to a gearshifting mode withoverstroke according to the invention,

FIGS. 16-18 are block diagrams relating to some multi-gearshifting modesaccording to the invention,

FIG. 19 is a block diagram relating to a position maintaining modeaccording to the invention,

FIGS. 20-23 show a derailleur according to a first embodiment of theinvention,

FIGS. 24-27 show a derailleur according to a second embodiment of theinvention, and

FIGS. 28-40 show a derailleur according to a third embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Introduction

In one aspect, the invention relates to a derailleur of a bicyclegearshift, comprising:

-   -   a support unit, configured to be mounted on a bicycle frame at        an assembly of coaxial toothed wheels of the gearshift,    -   a mobile unit, comprising a chain guide,    -   primary actuation means configured to move the mobile unit with        respect to the support unit so as to impart onto the chain guide        a primary displacement having at least a component in axial        direction with respect to an axis of the assembly of toothed        wheels,

characterized by further comprising:

-   -   secondary actuation means configured to move the mobile unit        with respect to the support unit so as to impart onto the chain        guide a secondary displacement having at least a component in        radial direction with respect to the axis of the assembly of        toothed wheels, wherein the secondary actuation means are        capable of moving the mobile unit independently of the primary        actuation means.

Thanks to the secondary displacement independent of the primarydisplacement, it is possible to ensure that the mobile unit—and inparticular the chain guide—is always in the ideal position with respectto the assembly of toothed wheels. Typically, during gearshifting itwill be in a position relatively radially close to the toothed wheels,while during normal travel it will be in a position relatively radiallyfar. Moreover, the radial distance (both in close position and in farposition) can be suitably selected according to the diameter of thetoothed wheel on which the chain is engaged, thus being able to alwaysbe the one most suited to the circumstances at hand. More in general, itis possible to change the radial distance during normal travel and/orgearshifting.

In this way it is possible to speed up gearshifting without necessarilyhaving to increase the speed of a motor of the primary actuation means,because the chain can be kept as close as possible to the toothed wheelsduring gearshifting.

Typically, the primary displacement imparted by the primary actuationmeans also has a component in the radial direction and/or a component inthe circumferential direction, with respect to the axis of the assemblyof toothed wheels.

The secondary displacement imparted by the secondary actuation means hasa possible component in the circumferential direction, however it has nocomponent in the axial direction.

Preferably, the derailleur is a rear derailleur.

Preferably:

-   -   the support unit comprises a support body and a first fixing        unit, for mounting the support body on the frame;    -   the mobile unit comprises a mobile body and a second fixing        unit, for mounting the chain guide on the mobile body;    -   a chain tensioning spring is provided for in at least one of the        first fixing unit and the second fixing unit, the chain        tensioning spring determining a setup of the chain guide when        engaged with a bicycle transmission chain;    -   the secondary actuation means comprise a linkage for adjusting        the preload of the chain tensioning spring, so as to determine a        change in the setup of the chain guide that involves the        secondary displacement of the chain guide.

As stated above, the chain tensioning spring (or springs) is responsiblefor the dynamic equilibrium that determines the setup of the chain guideand eventually the setup of the chain, which also comprises the radialdistance of the chain guide from the axis of the assembly of toothedwheels. Thus by changing the preload of this spring (or of at least oneof these springs, if there is more than one) the desired change of theposition of the chain guide with respect to the axis of the assembly oftoothed wheels is caused.

Preferably, the derailleur is of the articulated parallelogram type,with one fixed side and one mobile side opposite the fixed side andconnected to it by two connecting rods of equal length, wherein thefixed side is formed by the support body and the mobile side is formedby the mobile body. However, the invention is also applicable toderailleurs with a different configuration.

In a preferred embodiment:

-   -   the first fixing unit comprises:        -   a pivot intended to be mounted fixed on the frame, the            support body and the chain tensioning spring being rotatably            mounted on the pivot,        -   a first ring, rotatably mounted on the pivot, provided with            a tooth for resting on the frame and with a seat in            engagement with a first end of the chain tensioning spring;

and furthermore:

-   -   the linkage for adjusting the preload of the chain tensioning        spring comprises:        -   a second ring, rotatably mounted in the support body and on            the pivot, provided with a seat in engagement with a second            end of the chain tensioning spring,        -   a toothed sector formed on the second ring,        -   a worm screw in engagement with the toothed sector.

In this embodiment, therefore, the chain tensioning spring on which thelinkage for adjusting the preload acts is arranged in the first fixingunit, thus in the support unit. In this condition, the additionalcomponents necessary in the derailleur to implement the invention aresubstantially all provided in the support unit, i.e. in a unit mounteddirectly on the frame of the bicycle and subject to limited movementsand deformations; in this way, therefore, there is the dual advantagethat the bulk of the derailleur is not substantially increased and thatthe secondary actuation means are in a relatively protected positionagainst possible impacts during use of the bicycle.

In an alternative embodiment:

-   -   the second fixing unit comprises:        -   a pivot mounted in the mobile body, the chain guide and the            chain tensioning spring being rotatably mounted on the            pivot,        -   a seat formed in the chain guide, in engagement with a first            end of the spring;

and wherein:

-   -   the linkage for adjusting the preload of the chain tensioning        spring comprises:        -   a ring, rotatably mounted in the mobile body and provided            with a seat in engagement with a second end of the chain            tensioning spring,        -   a toothed sector formed on the ring,        -   a worm screw in engagement with the toothed sector.

In this embodiment, therefore, the chain tensioning spring on which thelinkage for adjusting the preload acts is arranged in the second fixingunit, thus in the mobile unit. In this condition, the additionalcomponents necessary in the derailleur to implement the invention aresubstantially all provided in the mobile unit, i.e. in a unit mounted insignificantly protruding position with respect to the frame of thebicycle; in this way, therefore, it is easier to gain access thereto,for adjustments, calibrations, maintenance, cleaning and the like.

In a preferred embodiment, the primary actuation means comprise a firstelectric motor and the secondary actuation means comprise a secondelectric motor.

The use of separate motors, able to be driven independently for thefirst and the second actuation means allows the maximum freedom inchoosing the motors most suitable for the specific conditions of use. Inparticular, it is possible to keep the conventional configuration forthe primary actuation means, including the motor. It also makes it easyto obtain the independence of the primary and secondary displacements.

With this embodiment it is also possible to have simultaneousoperation—where necessary—of the primary and secondary actuation means.

In an alternative embodiment, the primary actuation means and thesecondary actuation means comprise a single shared electric motor, witha transmission being provided for having a primary output and asecondary output respectively associated with the primary actuationmeans and with the secondary actuation means. Also with this embodimentit is possible, although more complicated, to have simultaneousoperation of the primary and secondary actuation means.

The use of a single motor for both the primary and secondary actuationmeans makes it possible to avoid the weight, the bulk and the cost of asecond motor and of the relative control systems. Indeed, the weight,the bulk and the cost of an electric motor with the suitable power aregreater than those of the transmission.

Preferably, the transmission comprises:

-   -   a primary shaft set in rotation by the single electric motor,    -   a primary toothed wheel, fixedly fitted on the primary shaft,    -   a first secondary shaft and a second secondary shaft, parallel        to one another and to the primary shaft,    -   a first secondary toothed wheel, fixedly fitted on the first        secondary shaft,    -   a second secondary toothed wheel, fixedly fitted on the second        secondary shaft,    -   an auxiliary toothed wheel, mounted in an axially mobile manner        along an auxiliary axis parallel to the primary and secondary        shafts, in meshed engagement permanently with the primary        toothed wheel and selectively with one and/or the other of the        secondary toothed wheels.

This configuration can be easily implemented, obtaining a simple andreliable and very compact transmission.

Preferably, a reduction stage is arranged between the electric motor andthe primary shaft, to allow an ordinary electric motor (that operates ata relatively high rotation speed) to be used, although at the twoprimary and secondary outputs a much lower angular speed is necessary.

Preferably, the auxiliary toothed wheel is fixedly fitted on anauxiliary shaft, rotatably carried by a slide guided in a mobile manneralong the auxiliary axis.

More preferably, said slide is actuated by an electromagnetic actuator.

The electromagnetic actuator preferably comprises a push-pullelectromagnet.

Alternatively, the auxiliary toothed wheel is axially slidably fitted ona non-sliding auxiliary shaft extending along the auxiliary axis, and isactuated for this purpose by a suitable actuator.

In one aspect, the invention relates to a method for electronicallycontrolling a bicycle gearshift comprising a support unit configured tobe mounted on a bicycle frame at an assembly of coaxial toothed wheelsof the gearshift and a mobile unit comprising a chain guide, said methodcomprising the steps of:

-   -   moving the mobile unit with respect to the support unit so as to        impart onto the chain guide a primary displacement having at        least a component in axial direction with respect to an axis of        the assembly of toothed wheels,

characterized by further comprising the step of:

-   -   moving the mobile unit with respect to the support unit so as to        impart onto the chain guide a secondary displacement having at        least a component in radial direction with respect to the axis        of the assembly of toothed wheels, wherein said step of moving        the mobile unit with respect to the support unit so as to impart        onto the chain guide a secondary displacement is carried out        independently of said step of moving the mobile unit with        respect to the support unit so as to impart onto the chain guide        a primary displacement.

Preferably the method comprises, in order to carry out gearshifting, thesteps of:

a) driving the primary actuation means to displace the mobile unitbetween a position of engagement of a starting toothed wheel of theassembly of toothed wheels and a position of engagement of a destinationtoothed wheel of the assembly of toothed wheels; and

b) driving the secondary actuation means to displace the mobile unitradially with respect to an axis of the assembly of toothed wheels.

More specifically, the method comprises, in order to carry outgearshifting, the step of:

a) driving the primary actuation means to displace the mobile unitbetween a position of engagement of a starting toothed wheel of theassembly of toothed wheels and a position of engagement of a destinationtoothed wheel of the assembly of toothed wheels;

and at least one of the steps of:

b1) driving the secondary actuation means to bring the mobile unitradially closer to the assembly of toothed wheels; and

b2) driving the secondary actuation means to bring the mobile unitradially farther from the assembly of toothed wheels.

In a preferred embodiment, the three steps a), b1) b2) are all providedfor. However, considering that the toothed wheels have differentdiameters, for some or all gearshifting it is possible to omit one ofthe two displacements in the radial direction of steps b1) and b2). Inparticular, if the gearshifting is downward gearshifting, from a toothedwheel having a larger diameter to a toothed wheel having a smallerdiameter, the primary displacement obtained in step a) already involvesadequately bringing radially farther from the destination toothed wheel,so that step b2) can be omitted. Vice-versa, if the gearshifting isupward gearshifting, from a toothed wheel having a smaller diameter to atoothed wheel having a larger diameter, the primary displacementobtained in step a) already involves adequately bringing radially closerto the destination toothed wheel, so that step b1) can be omitted.

In embodiments, steps b1) where provided for, a) and b2) where providedfor, are sequential to each other.

In embodiments, step b1) is at least partially simultaneous with stepa), and step b2) is sequential to steps a) and b1).

In embodiments, step b1) is at least partially simultaneous with step a)and/or step b2) is at least partially simultaneous with step a).

Step a) can comprise a step of driving the primary actuation means todisplace the mobile unit between a position of engagement of a startingtoothed wheel of the assembly of toothed wheels and a temporary positiondifferent from a position of engagement of a destination toothed wheelof the assembly of toothed wheels.

More preferably, a step of staying of the mobile unit in the temporaryposition for a predetermined time period is further comprised.

Even more preferably, a step of driving the primary actuation means todisplace the mobile unit from the temporary position to a position ofengagement of the destination toothed wheel is further comprised.

In this way it is possible to carry out so-called gearshifting “withoverstroke”, for example wherein the chain is brought beyond thedestination toothed wheel for a certain time and then, when actuallyengaged, it is brought back on the destination toothed wheel.

The stay in temporary position takes place deliberately for thepredetermined time period, namely measures are taken, or means areimplemented, suitable for monitoring the passing of the predeterminedtime period.

Alternatively or in addition, step a) can comprise driving the primaryactuation means to displace the mobile unit between a position ofengagement of a starting toothed wheel of the assembly of toothed wheelsand a position of engagement of a destination toothed wheel of theassembly of toothed wheels not immediately adjacent to the startingtoothed wheel in the assembly of toothed wheels, directly or with astop/stops at the/each intermediate toothed wheel between the startingtoothed wheel and the destination toothed wheel.

In this way, multi-gearshifting is obtained in which the secondarydisplacement in the radial direction occurs only at the start and/or atthe end of the multi-gearshifting.

Alternatively, multi-gearshifting can be obtained as a series ofindividual gearshiftings close together in time, namely with secondarydisplacement in the radial direction, of bringing closer and/or farther,also at the or each intermediate toothed wheel and not only at thestarting toothed wheel and/or the destination toothed wheel.

In particular, step a) can comprise the steps of:

a1) driving the primary actuation means to displace the mobile unitbetween a position of engagement of the starting toothed wheel and aposition of engagement of a first toothed wheel intermediate between thestarting toothed wheel and the destination toothed wheel;

a2) driving the primary actuation means to displace the mobile unitbetween the position of engagement of the first intermediate toothedwheel and the position of engagement of the destination toothed wheel;

and between said steps a1) and a2) there is at least one of the stepsb11) and b21) of:

b11) driving the secondary actuation means to bring the mobile unitradially closer to the first intermediate toothed wheel;

b21) driving the secondary actuation means to bring the mobile unitradially farther from the first intermediate toothed wheel.

In case of triple gearshifting, step a2) comprises the steps of:

a21) driving the primary actuation means to displace the mobile unitbetween the position of engagement of the first intermediate toothedwheel and a position of engagement of a second intermediate toothedwheel of the assembly of toothed wheels, the second intermediate toothedwheel being intermediate between the first intermediate toothed wheeland the destination toothed wheel; and

a22) driving the primary actuation means to displace the mobile unitbetween the position of engagement of the second intermediate toothedwheel and the position of engagement of the destination toothed wheel,

and between said steps a21) and a22) there is preferably at least one ofthe steps b12) and b22) of:

b12) driving the secondary actuation means to bring the mobile unitradially closer to the second intermediate toothed wheel,

b22) driving the secondary actuation means to bring the mobile unitradially farther from the second intermediate toothed wheel.

Similarly, it is possible to carry out quadruple, quintuplegearshifting, etc. in a recursive manner.

Alternatively or in addition to carrying out gearshifting as describedabove, the method preferably comprises, during normal travel, the stepsof:

c) checking whether the current position of the mobile unit with respectto the assembly of toothed wheels corresponds to a nominal position ofengagement of a motion transmission chain with a preselected toothedwheel, and in the negative case carrying out at least one of the stepsof:

d) driving the primary actuation means to displace the mobile unitbetween the current position and the nominal position of engagement; and

e) driving the secondary actuation means to displace the mobile unitbetween the current position and the nominal position of engagement.

Said checking step c) is carried out through at least one sensor,preferably at least one angular position sensor, more preferably of theabsolute type, even more preferably at least one Hall effect encoder.

Checking step c) can be carried out cyclically at a predeterminedfrequency and/or after a predetermined time since gearshifting from astarting toothed wheel to said preselected toothed wheel as destinationtoothed wheel and/or upon request by the cyclist.

In one aspect, the invention relates to a bicycle electronic gearshiftcomprising at least one derailleur, preferably as described above, and acontroller configured to carry out the steps of the method outlinedabove.

The controller can be internal to the derailleur or external to thederailleur.

The controller is made through at least one processor—typically amicroprocessor or a microcontroller—being suitable for implementing oneor more steps of the method, providing for suitable procedures and/orhardware modules, software and/or firmware.

In the present description and in the attached claims, therefore, undercontroller a logic unit shall be meant, which can however be formed ofplural physical units, in particular of one or more distributedmicroprocessors that can be contained in one or more casings togetherwith one or more of the other components of the bicycle gearshift.

DETAILED DISCLOSURES

The invention is shown wholly schematically in FIG. 1.

First an assembly of toothed wheels RD of the bicycle transmission isshown. The toothed wheels RD are configured to be mounted in a per seknown manner on a bicycle frame T (see for example FIG. 20), typicallyat the axle of the pedal cranks in the front gearshift assembly or atthe axle of the rear wheel in the rear gearshift assembly. The number oftoothed wheels RD shown is merely an example.

The toothed wheels RD are coaxial to each other, the axis of theassembly of toothed wheels RD being indicated with Z. The toothed wheelsRD have a different diameter, and in particular decreasing from left toright in FIG. 1, however this is not strictly necessary. The toothedwheels RD have a distance along the axis Z, also known as pitch, that isconstant, but this is not strictly necessary.

A chain (not shown) of the transmission is in engagement with onetoothed wheel RD at a time during travel, according to the desired gearratio—said gear ratio being given by the number of teeth and thereforeby the diameter of the engaged toothed wheel RD, as well as in generalby the number of teeth and therefore by the diameter of the engagedtoothed wheel in a second assembly of toothed wheels of thetransmission.

A gearshift 1 allows the gear ratio to be changed by displacing thechain among the toothed wheels RD. Through gearshifting, the chain istaken from engagement with a starting toothed wheel RD to engagementwith a destination toothed wheel RD, and it can turn out to betemporarily engaged with two adjacent toothed wheels RD duringgearshifting.

The gearshift 1 comprises a derailleur 2 associated with the assembly oftoothed wheels RD—and a possible second derailleur (not shown)associated with the second assembly of toothed wheels of thetransmission.

The derailleur 2 comprises a support unit 3, configured to be mounted,in a fixed and per se known manner, on the frame T at the assembly oftoothed wheels RD.

The derailleur 2 further comprises a mobile unit 4, which is so mountedas to be mobile with respect to the support unit 3, and therefore mobilewith respect to the frame T, and in particular mobile with respect tothe assembly of toothed wheels RD.

The mobile unit 4 comprises a chain guide (not shown in FIG. 1) thatdetermines the position of the chain with respect to the assembly oftoothed wheels RD and therefore the toothed wheel RD with which thechain is in engagement.

The derailleur 2 further comprises primary actuation means 5 configuredto move the mobile unit 4 with respect to the support unit 3 so as toimpart thereon, and therefore to impart on the chain guide andeventually on the chain, a primary displacement in the axial directionwith respect to the axis Z of the assembly of toothed wheels RD, namelyalong the axis Z. In the following description, reference will sometimesbe made to the position and to the displacement of the mobile unit 4with respect to the toothed wheels RD, sometimes to the position and tothe displacement of the chain guide with respect to the axis Z,sometimes to other parts.

The primary displacement of the mobile unit 4 is shown schematically bythe double arrow between an example starting position of the mobile unit4, shown with a solid line, and an example destination position of themobile unit 4, shown with a dashed line and indicated as 4 a.

More in general, the primary displacement of the mobile unit 4 can have,besides the component in the axial direction, also a component in theradial direction and/or a component in the circumferential direction,namely it rotates around the toothed wheels RD. In other words, theprimary displacement of the mobile unit 4 can have components also alongthe axes X and Y shown in FIG. 1.

The derailleur 2 further comprises secondary actuation means 6configured to move the mobile unit 4 with respect to the support unit 3so as to impart onto the chain guide, and eventually onto the chain, asecondary displacement in the radial direction with respect to the axisZ of the assembly of toothed wheels RD, namely closer to or farther fromthe axis Z and therefore to/from the circumference of the toothed wheelsRD.

The secondary displacement of the mobile unit 4 is shown schematicallyby the double arrow between the example starting position of the mobileunit 4, shown with a solid line, and an example destination position ofthe mobile unit 4, shown with a chain dotted line and indicated as 4 b.

The secondary displacement imparted by the secondary actuation means 6can also have a possible component in the circumferential direction, butit does not have any component in the axial direction Z.

According to the invention, the secondary actuation means 6 are capableof moving the mobile unit 4 independently of the primary actuation means5.

Through a suitable choice among the primary displacement imparted by theprimary actuation means 5 and the secondary displacement imparted by thesecondary actuation means 6, or a suitable combination thereof, themobile unit 4 can be brought at any moment into virtually any positionwith respect to the assembly of toothed wheels RD.

Those skilled in the art will understand, in light of the followingdescription, that the primary displacement of the mobile unit 4 will belimited to a stroke extending between the two extreme toothed wheels RDof the assembly, or slightly beyond. The secondary displacement of themobile unit 4 will be limited to a stroke extending between a positionin close proximity to the circumference of the toothed wheel RD havingthe minimum diameter, and a position relatively far from thecircumference of the toothed wheel RD having maximum diameter, stillsufficiently close to keep the chain in engagement with such a toothedwheel RD having maximum diameter, and thus prevent the chain fromfalling.

In an electronically servo-assisted embodiment of the gearshift 1, theprimary actuation means 5 and the secondary actuation means 6 aredriven, independently—even if coordinately—, by a controller 7 of thebicycle gearshift 1.

The controller 7 is embodied by at least one processor—typically amicroprocessor or a microcontroller—suitable for implementing one ormore of the steps described herein, providing for suitable proceduresand/or hardware, software and/or firmware modules.

In the present description and in the attached claims, therefore, undercontroller 7 a logic unit is meant, which can however be formed ofplural physical units, in particular of one or more distributedmicroprocessors that can be contained in one or more casings togetherwith one or more of the other components of the bicycle gearshift.

The controller 7 can thus be internal to the derailleur 2 or external tothe derailleur 2, or partially internal and partially external thereto.

With reference to FIG. 2, a first gearshifting mode according to theinvention is shown. The gearshifting mode shown in FIG. 2 isparticularly suitable for implementation in a derailleur of the typeshown in FIGS. 28-40 described hereinafter, wherein the primaryactuation means 5 and the secondary actuation means 6 share a singleelectric motor, however it can also be implemented in a derailleur ofthe type shown in FIGS. 20-23 and in FIGS. 24-27 described hereinafter,wherein the primary actuation means 5 and the secondary actuation means6 have a respective electric motor.

In a step 1000, the controller 7 drives the secondary actuation means 6to bring the mobile unit 4 radially closer to the support unit 3, andtherefore to the assembly of toothed wheels RD.

In particular, in this step 1000 the mobile unit 4 starts from aposition (FIG. 3 for the case of upward gearshifting, and FIG. 8 for thecase of downward gearshifting) wherein it is relatively radially farfrom a starting toothed wheel RD, with which the chain is engaged, andis brought (FIG. 4 and FIG. 9) into a position wherein it is relativelyradially close to the starting toothed wheel RD.

The initial position (FIG. 3 and FIG. 8) of step 1000, relatively far,is such that the chain is not unduly stressed, and therefore normaltravel occurs as smoothly as possible. The final position (FIG. 4 andFIG. 9) of step 1000, relatively close, is such as to facilitate theengagement of the chain with the teeth of the destination toothed wheelRD—having a greater or smaller diameter, respectively, than the startingtoothed wheel RD in case of upward or downward gearshifting,respectively.

During step 1000, the mobile unit 4 can undergo a circumferentialdisplacement about the starting toothed wheel RD, but it is not moved inthe axial direction Z, namely the chain stays in engagement with thestarting toothed wheel RD.

In a subsequent step 1002, the controller 7 drives the primary actuationmeans 5 to move the mobile unit 4 axially along the assembly of toothedwheels RD (FIG. 5 and FIG. 10). In particular, in this step 1002 themobile unit 4 starts from a position axially at the starting toothedwheel RD, with which the chain is engaged, and is brought into aposition axially at the destination toothed wheel RD, with which it iswished for the chain to engage.

During step 1002, the mobile unit 4 can undergo a circumferentialdisplacement, and possibly also a displacement in the radial direction(as can be seen in FIG. 5 and in FIG. 10), but the main function of step1002 is to make it carry out the axial displacement up to thedestination toothed wheel RD.

Finally, in a step 1004, the controller 7 drives the secondary actuationmeans 6 to bring the mobile unit 4 radially farther from the assembly oftoothed wheels RD (FIG. 6 and FIG. 11). In particular, in this step 1004the mobile unit 4 starts from a position wherein it is relativelyradially close to the destination toothed wheel RD, with which the chainis now engaged, and it is brought into a position wherein it isrelatively radially far from the destination toothed wheel RD (FIG. 7and FIG. 12).

In a dual manner with respect to step 1000, the initial position of step1004, relatively close, is such as to facilitate the engagement of thechain with the teeth of the destination toothed wheel RD, while thefinal position of step 1004, relatively far, is such that the chain isnot unduly stressed, and therefore normal travel occurs in the smoothestpossible manner.

During step 1004, the mobile unit 4 can undergo a circumferentialdisplacement about the destination toothed wheel RD, but is not moved inthe axial direction Z, namely the chain stays in engagement with thedestination toothed wheel RD.

In step 1002 of moving the mobile unit 4 according to the primarydisplacement, like in the analogous ones of the figures describedhereinafter, the electric motor of the primary actuation means 5 isdriven based on the values of the table of command values described inthe introductory part. Namely, the controller 7 reads from the table ofcommand values the value associated with the destination toothed wheel,and drives the electric motor until such a value is reached. The drivingcan take place with a suitable speed and/or acceleration profile.

In steps 1000 and 1004 of moving the mobile unit 4 according to thesecondary displacement, like in the analogous ones of the figuresdescribed hereinafter, the electric motor of the secondary actuationmeans 6 is driven based on the values of an analogous table of commandvalues, and can be moved with a suitable speed and/or accelerationprofile.

The tables of command values can be combined in a single table ofcommand values having, for each toothed wheel RD, one, two or threeaxial position values (for the reasons that will become clearhereinafter) and two radial position values, one corresponding to theposition relatively close to the circumference of the toothed wheel RDand one corresponding to the position relatively far from thecircumference of the toothed wheel RD.

Considering that the toothed wheels RD have different diameters, forsome or all gearshifting one of the two displacements in the radialdirection can be omitted, namely step 1000 or step 1004 can be omitted.

In particular, in case of downward gearshifting, since one goes from astarting toothed wheel RD having a larger diameter to a destinationtoothed wheel RD having a smaller diameter, the position radially closeto the starting toothed wheel RD obtained with step 1000 can already besufficiently radially far from the destination toothed wheel RD, oncethe step 1002 of primary displacement has been carried out, so that thechain is in optimal condition for normal travel. In this case, step 1004can be omitted.

Vice-versa, in case of upward gearshifting, since one goes from astarting toothed wheel RD having a smaller diameter to a destinationtoothed wheel RD having a larger diameter, step 1000 can be omitted. Inthis case, step 1002 of primary displacement takes place from theposition radially far from the starting toothed wheel RD, a positionthat may be sufficiently radially close to the destination toothed wheelRD for the correct engagement of the chain with such a destinationtoothed wheel RD.

With reference to FIG. 13, a second gearshifting mode is shown. Thegearshifting mode shown in FIG. 13 is particularly suitable forimplementation in a derailleur of the type shown in FIGS. 20-23 and inFIGS. 24-27, wherein the primary actuation means 5 and the secondaryactuation means 6 each have a respective electric motor. However, it canalso be implemented in a derailleur of the type shown in FIGS. 28-40.

The gearshifting mode of FIG. 13 differs from that of FIG. 2 in thatstep 1010 of driving the secondary actuation means 6 to bring the mobileunit 4 radially closer to the assembly of toothed wheels RD takes placein parallel to, and at least partially simultaneously with, the step1012 of driving the primary actuation means 5 to displace the mobileunit 4 axially from the starting toothed wheel RD to the destinationtoothed wheel RD.

Step 1014 of driving the secondary actuation means 6 to bring the mobileunit 4 radially farther from the assembly of toothed wheels RD, on theother hand, takes place at the end of such steps carried out in parallel1010 and 1012.

In this way, the actual gearshifting, namely the displacement of thechain from engagement with the starting toothed wheel RD to engagementwith the destination toothed wheel RD, can be carried out with extremeprecision and speed, in that the chain can be displaced obliquely withrespect to the toothed wheels RD keeping it at an even exactly constantdistance therefrom.

With reference to FIG. 14, a third gearshifting mode is shown. Thegearshifting mode of FIG. 14 differs from those of FIGS. 2 and 13 inthat the driving of the secondary actuation means 6 in both steps 1020and 1024 of bringing the mobile unit 4 radially closer to the assemblyof toothed wheels RD, and of bringing the mobile unit 4 radially fartherfrom the assembly of toothed wheels RD, takes place in parallel to, andat least partially simultaneously with, the step 1022 of driving theprimary actuation means 5 to displace the mobile unit 4 axially from thestarting toothed wheel RD to the destination toothed wheel RD.

Also with this mode, gearshifting can be carried out with extremeprecision and speed, controlling the radial position and the axialposition of the mobile unit at every moment of its movement.

In step 1002, 1012, 1022 of primary displacement in the axial direction,the command value associated with a same destination toothed wheel RDcan be different for the case of upward gearshifting, wherein thestarting toothed wheel RD is of a smaller diameter than the destinationtoothed wheel RD, and for the case of downward gearshifting, wherein thestarting toothed wheel RD is of a larger diameter than the destinationtoothed wheel RD. In this way it is possible to implement so-calledgearshifting with “overstroke”, namely to bring the chain slightlyaxially beyond the destination toothed wheel RD, or slightly axiallybefore the destination toothed wheel RD, so as to facilitate themechanical engagement thereof. Of course, the extreme toothed wheels RDof the assembly will have a single associated command value.

In an embodiment, shown in FIG. 15, in step 1002, 1012, 1022 of primarydisplacement in the axial direction, the mobile unit 4 is initiallybrought—in a step 1030—into the aforementioned temporary axial oroverstroke position, it is maintained here temporarily—in a step1032—and then is brought into the axial position at the destinationtoothed wheel RD—in a step 1034.

Preferably, when step 1022 of primary displacement in the axialdirection of the embodiment of FIG. 14 is dealt with, step 1030 of axialpositioning in overstroke position preferably takes place in parallelto, and at least partially simultaneously with, the step 1020 ofbringing radially closer, subsequently the step 1032 of waiting inoverstroke position and the step 1034 of final axial displacement takeplace and, simultaneously or subsequently, the step 1024 of bringingradially farther takes place.

In step 1002, 1012, 1022 of primary displacement in the axial direction,the mobile unit 4 can be displaced from a starting toothed wheel RD to adestination toothed wheel RD not immediately adjacent to the startingtoothed wheel RD, in order to carry out multi-gearshifting.

Such a primary displacement can occur directly as shown by step 1040 ofFIG. 16, or it can occur in plural steps, with intermediatedisplacement—and possible stop—at the or each intermediate toothed wheelRD between the starting toothed wheel RD and the destination toothedwheel RD, as shown in FIG. 17 wherein triple gearshifting is shown as anexample with three axial displacements 1042, 1044, 1046 of the mobileunit 4 through the primary actuation means 5: in step 1042 a primarydisplacement occurs from the starting toothed wheel RD to a firstintermediate toothed wheel RD—preferably immediately adjacent thereto—,in step 1044 a primary displacement occurs from the first intermediatetoothed wheel RD to a second intermediate toothed wheel RD—preferablyimmediately adjacent thereto—and in step 1046 a primary displacementoccurs from the second intermediate toothed wheel RD to the destinationtoothed wheel RD.

In both of these modes, during multi-gearshifting, the secondarydisplacement in the radial direction takes place only at the startand/or at the end of multi-gearshifting.

Alternatively, the multi-gearshifting can occur with a series of singlegearshiftings according to the invention close together in time, namelywith two or more primary displacements through the primary actuationmeans 5—according to whether there are one or more intermediate toothedwheels RD between the starting toothed wheel RD and the destinationtoothed wheel RD—, and one or more secondary displacements through thesecondary actuation means 6 at the or each intermediate toothed wheelRD.

The secondary displacements through the secondary actuation means 6 canbe displacements bringing radially closer and/or farther.

For example, as shown in FIG. 18 for the case of triple gearshifting,there can be an initial step 1050 of primary displacement from thestarting toothed wheel RD to a first intermediate toothed wheelRD—preferably immediately adjacent thereto—, a step 1052 of secondarydisplacement in the radial direction at the first intermediate toothedwheel RD, a step 1054 of primary displacement from the firstintermediate toothed wheel RD to a second intermediate toothed wheelRD—preferably immediately adjacent thereto—, a step 1056 of secondarydisplacement in the radial direction at the second intermediate toothedwheel RD, and a final step 1058 of primary displacement from the secondintermediate toothed wheel RD to the destination toothed wheel RD.

As stated above, the secondary displacements at the intermediate toothedwheels RD of steps 1052, 1056 can be displacements bringing radiallycloser, bringing radially farther, or bringing radially farther andsubsequently bringing radially closer.

If the primary displacements of steps 1050, 1054, 1056 are exclusivelyaxial or if in any case the possible radial component is negligible,then in case of upward multi-gearshifting, the secondary displacementsat the intermediate toothed wheels RD of steps 1052, 1056 can bedisplacements bringing radially farther, while in case of downwardmulti-gearshifting, the secondary displacements at the intermediatetoothed wheels RD of steps 1052, 1056 can be displacements bringingradially closer.

Although in FIG. 18 the steps of axial and radial displacement are shownas consecutive, and therefore gearshifting occurs in an analogous mannerto FIG. 2, these steps can also be at least partially simultaneous,analogously to what is shown in FIGS. 13 and 14.

In all cases, also in multi-gearshifting there can be positioning of themobile unit 4 in overstroke position, preferably temporary and withdefinitive displacement in position of engagement with the or eachintermediate toothed wheel RD, as described with reference to FIG. 15.

With reference to FIG. 19, a mode of maintaining the optimal position ofthe mobile unit 4 during travel is shown, that can be achieved accordingto the invention.

In a step 1100, the controller 7 checks whether the current position ofthe mobile unit 4 corresponds to the nominal position corresponding tothe current gear ratio. In particular, as explained above, the nominalposition is relatively radially far from the toothed wheel RD currentlyengaged.

In the positive case, the procedure ends.

In the negative case, the controller 7 drives the primary actuationmeans 5 in a step 1102, drives the secondary actuation means 6 in a step1104, or drives both the primary actuation means 5 and the secondaryactuation means 6 in a step 1106 to displace the mobile unit 4 in theaxial direction and/or in the radial direction with respect to the axisZ of the assembly of toothed wheels RD and bring it back into thenominal position. Step 1102, step 1104 or step 1106 is carried outaccording to the offset between the nominal position and the currentposition of the mobile unit 4.

Step 1100 of checking is carried out through at least one sensor,preferably at least one angular position sensor, more preferably of theabsolute type, even more preferably at least one Hall effect encoder.

Such an angular position sensor between a first and a second partcapable of a relative rotation movement about a given axis comprises forexample, in a per se known way and described for example in EP 1 279 929A2, a magnetized element fixedly connected to one of said first andsecond part, and at least one pair of Hall effect sensors arrangedangularly offset from one another with respect to said given axis andfixedly connected to the other of said first and second part; said Halleffect sensors being sensitive to the presence of said magnetizedelement so as to generate respective output signals with variable valuesin a continuous field, the values of said respective output signalsunambiguously identifying the relative position of said first and secondpart with respect to said given axis. The values of the output signalsalso unambiguously identify the direction of rotation of the first andsecond part with respect to the axis and the angular rotation speedand/or acceleration.

Step 1100 of checking can be carried out cyclically at a predeterminedfrequency, for example every 4 seconds.

Alternatively, step 1100 of checking can be carried out after apredetermined time since a gearshifting, for example 1 second, when itis more likely that involuntary displacements of the mobile unit 4 mightoccur—as described in the patent application published under US2014/0032067 of the Applicant.

Alternatively or in addition, step 1100 of checking can be carried outupon request by the cyclist, for example because he/she has the feelingthat the engagement of the chain is not smooth.

Also to carry out steps 1102, 1104 and 1106 the controller 7 will referto the table(s) of command values described above.

Some embodiments of derailleur suitable for implementing what statedabove will now be described. The derailleur being referred to is a rearderailleur. Hereinafter, specific reference numerals will be used foreach embodiment.

With reference to FIGS. 20-23, a derailleur 13 according to a firstembodiment of the invention comprises a support unit 20, configured tobe mounted on the frame T of the bicycle, at the assembly of toothedwheels RD, and a mobile unit 50, comprising a chain guide 52.

The derailleur 13 also comprises primary actuation means 70 configuredto move the mobile unit 50 with respect to the support unit 20, so as toimpart onto the chain guide 52 a primary displacement having at least acomponent in axial direction with respect to the axis Z of the assemblyof toothed wheels RD.

The derailleur 13 also comprises secondary actuation means 80 configuredto move the mobile unit 50 with respect to the support unit 20, so as toimpart onto the chain guide 52 a secondary displacement having at leasta component in radial direction with respect to the axis Z of theassembly of toothed wheels RD. The secondary actuation means 80, as willbe explained hereafter, are capable of moving the mobile unit 50independently of the primary actuation means 70.

The support unit 20 comprises a support body 21 and a first fixing unit23, for mounting the support unit 21 on the frame T of the bicycle. Themobile unit 50 comprises, in addition to the chain guide 52, a mobilebody 51 and a second fixing unit 53, for mounting the chain guide 52 onthe mobile body 51.

In the first fixing unit 23, a chain tensioning spring 25 is provided.

The primary actuation means 70 provide for an articulated quadrilaterallinkage between the support body 21 and the mobile body 51, which areconnected together through a pair of parallel connecting rods 71, 72,articulated both to the support body 21 at pivots 73, 74, and to themobile body 51, at pivots 75, 76. An electric motor 77 is mounted on thepivot 73 (cradle-shaped, for receiving the motor 77) and has a shaft 78engaged in a bushing 79 mounted on the pivot 76, diagonally opposite thepivot 73. Reference numeral 77 a indicates a cable for power supply andthe control signal of the motor 77.

The motor 77 is thus suitable for imposing an approach/distancing of thebushing 79 to the motor 77 and consequently a lengthening/shortening ofthe diagonal of the articulated quadrilateral linkage between the twoopposite pivots 73, 76 and therefore a deformation of the articulatedquadrilateral linkage itself. This deformation in turn determines adisplacement of the mobile body 51 with respect to the support body 21and thus the primary displacement of the chain guide 52 with respect tothe axis Z of the assembly of toothed wheels RD.

The first fixing unit 23 comprises a pivot, formed by two threadedelements 26 a, 26 b coaxial to one another, intended to be mounted fixedon the frame T; the support body 21 and the chain tensioning spring 25are rotatably mounted on the pivot 26 a, 26 b through interposition of asliding bearing 27. The first fixing unit 23 also comprises a first ring28, rotatably mounted on the pivot 26 a, 26 b, provided with a tooth 29for resting on the frame T and with a seat 30 in engagement with a firstend of the chain tensioning spring 25.

The secondary actuation means 80 comprise a second ring 81, rotatablymounted in the support body 21 and on the pivot 26 a, 26 b and providedwith a seat 82 in engagement with a second end of the chain tensioningspring 25. The secondary actuation means 80 also comprise a toothedsector 83 formed on the second ring 81, and a worm screw 84 inengagement with the toothed sector 83.

The worm screw 84 is set in rotation by an electric motor 85, through areduction stage 86, comprising toothed wheels of different diameterengaged with each other in succession, so as to determine the desiredgear ratio between the motor 85 and the worm screw 84.

The chain guide 52 comprises a pair of wheels 54, 55, idle mounted on anarm 56. The second fixing unit 53 comprises a pivot 57 fixedly connectedto the arm 56 of the chain guide 52 and rotatably mounted in the mobilebody 51; a torsion spring 58 is mounted on the pivot 57, with a firstend inserted in a seat 59 formed in an insert 63 firmly fixed in themobile body 51 and a second end inserted in a seat 60 formed on the arm56.

The spring 58, like the spring 25, contributes to tensioning the chain.More specifically, the two springs 25 and 58 counteract each other: thespring 25 tends to lengthen the path of the chain angularly pushing themobile body 51—namely, tending to rotate the mobile body 51 about thepivot 26 a, 26 b in the direction M—so as to push the chain guide 52radially away from the assembly of toothed wheels RD; the spring 58, onthe other hand, tends to lengthen the path of the chain by angularlypushing the chain guide 52 in the direction N so as to push the wheel 54radially towards the assembly of toothed wheels RD. The setup of thechain is thus in equilibrium between the thrusts of these springs 25 and58, and according to this setup the chain guide 52 is more or lessradially close to the axis Z of the assembly of toothed wheels RD.

By acting on the motor 85 of the secondary actuation means 80 it ispossible to angularly displace the seat 82 of the second end of thespring 25, thus changing the preload of the spring 25 itself. Therefore,the second ring 81, the seat 82, the toothed sector 83 and the wormscrew 84 form a linkage for adjusting the preload of the chaintensioning spring 25, capable of determining a change in the setup ofthe chain guide 52 that involves the secondary displacement of the chainguide 52, having at least a component in radial direction with respectto the axis Z of the assembly of toothed wheels RD.

On the other hand, by acting on the motor 77 of the primary actuationmeans 70, as described earlier, the primary displacement of the chainguide 52 with respect to the axis Z of the assembly of toothed wheelsRD, i.e. the displacement necessary to obtain gearshifting, is obtainedby displacing the chain from one of the toothed wheels RD to another.

The two displacements of the chain guide 52, the primary displacement(responsible for gearshifting) and the secondary displacement(responsible for the radial distance of the chain guide from the axisZ), are thus obtained totally independently of each other, thanks to theprimary actuation means 70 and secondary actuation means 80. It thusbecomes possible to determine the optimal distance of the chain guide 52from the axis Z in every situation, of travel or of gearshifting.

This result has been obtained, in accordance with the first embodimentshown in FIGS. 20 to 23 and just described, by providing for thesecondary actuation means 80 to act through their motor 85 on the spring25 of the first fixing unit 23.

A second embodiment of the invention is shown in FIGS. 24 to 27.

With reference to these figures, a derailleur 113 comprises a supportunit 120, configured to be mounted on the frame T of the bicycle, at theassembly of toothed wheels RD of the gearshift 1, and a mobile unit 150,comprising a chain guide 152.

The derailleur 113 also comprises primary actuation means 170 configuredto move the mobile unit 150 with respect to the support unit 120, so asto impart onto the chain guide 152 a primary displacement having atleast a component in axial direction with respect to the axis Z of theassembly of toothed wheels RD.

The derailleur 113 also comprises secondary actuation means 180configured to move the mobile unit 150 with respect to the support unit120, so as to impart onto the chain guide 152 a secondary displacementhaving at least a component in radial direction with respect to the axisZ of the assembly of toothed wheels RD. The secondary actuation means180, as will be explained hereafter, are capable of moving the mobileunit 150 independently of the primary actuation means 170.

The support unit 120 comprises a support body 121 and a first fixingunit 123, for mounting the support unit 121 on the frame T. The mobileunit 150 comprises, as well as the chain guide 152, a mobile body 151and a second fixing unit 153, for mounting the chain guide 152 on themobile body 151.

In the first fixing unit 123 a chain tensioning spring 125 is provided.

The primary actuation means 170 provide for an articulated quadrilaterallinkage between the support body 121 and the mobile body 151, which areconnected together through a pair of parallel connecting rods 171, 172,articulated both to the support body 121 at pivots 173, 174, and to themobile body 151, at pivots 175, 176. An electric motor 177 is mounted onthe pivot 173 (shaped like a cradle, for receiving the motor 177) andhas a shaft 178 engaged in a bushing 179 mounted on the pivot 176,diagonally opposite the pivot 173. Reference numeral 177 a indicates acable for power supply and the control signal of the motor 177. Themotor 177 is thus suitable for imposing an approach/distancing of thebushing 179 to the motor 177 and consequently a lengthening/shorteningof the diagonal of the articulated quadrilateral linkage between the twoopposite pivots 173, 176 and therefore a deformation of the articulatedquadrilateral linkage itself. This deformation in turn determines adisplacement of the mobile body 151 with respect to the support body 121and thus the primary displacement of the chain guide 152 with respect tothe axis Z of the assembly of toothed wheels RD.

The first fixing unit 123 comprises a pivot, formed by two threadedelements 126 a, 126 b coaxial to one another, intended to be mountedfixed on the frame T; the support body 121 and the chain tensioningspring 125 are rotatably mounted on the pivot 126 a, 126 b, throughinterposition of a sliding bearing 127. The first fixing unit 123 alsocomprises a first ring 128, rotatably mounted on the pivot 126 a, 126 b,provided with a tooth 129 for resting on the frame T and with a seat 130in engagement with a first end of the chain tensioning spring 125.

Differently from the derailleur 13, in the derailleur 113 the second endof the spring 125 is engaged in a seat 131, formed in the support body121.

The chain guide 152 comprises a pair of wheels 154, 155, idle mounted onan arm 156. The second fixing unit 153 comprises a pivot 157 fixedlyconnected to the mobile body 151, on which pivot 157 the arm 156 of thechain guide 152 is rotatably mounted; a torsion spring 158 is mounted onthe pivot 157, with a second end inserted in a seat 160 formed on thearm 156.

The secondary actuation means 180 comprise a second ring 191, rotatablymounted in the mobile body 151 and on the pivot 157 and provided with aseat 192 in engagement with a second end of the spring 158. Thesecondary actuation means 180 also comprise a toothed sector 193 formedon the second ring 191, and a worm screw 194 in engagement with thetoothed sector 193.

The worm screw 194 is set in rotation by an electric motor 195, througha reduction stage 196, comprising toothed wheels of different diameterengaged with one another in succession, so as to determine the desiredgear ratio between the motor 195 and the worm screw 194. Referencenumeral 195 a indicates a cable for power supply and the control signalof the motor 195.

The spring 158, like the spring 125, contributes to tensioning thechain. More specifically, the two springs 125 and 158 counteract eachother: the spring 125 tends to lengthen the path of the chain angularlypushing the mobile body 151—namely, tending to rotate the mobile body151 about the pivot 126 a, 126 b in the direction M—so as to push thechain guide 152 radially away from the assembly of toothed wheels RD;the spring 158, on the other hand, tends to lengthen the path of thechain by angularly pushing the chain guide 152 in the direction N so asto push the wheel 154 radially towards the assembly of toothed wheelsRD. The setup of the chain is thus in equilibrium between the thrusts ofthese springs 125 and 158, and according to this setup the chain guide152 is more or less radially close to the axis Z of the assembly oftoothed wheels RD.

By acting on the motor 195 of the secondary actuation means 180 it ispossible to angularly displace the seat 192 of the second end of thespring 158, thus changing the preload of the spring 158 itself.Therefore, the second ring 191, the seat 192, the toothed sector 193 andthe worm screw 194 form a linkage for adjusting the preload of the chaintensioning spring 158, capable of determining a change in the setup ofthe chain guide 152 that involves the secondary displacement of thechain guide 152, having at least a component in radial direction withrespect to the axis Z of the assembly of toothed wheels RD.

On the other hand, by acting on the motor 177 of the primary actuationmeans 170, as described earlier, the primary displacement of the chainguide 152 with respect to the axis Z of the assembly of toothed wheelsRD, i.e. the displacement necessary to obtain gearshifting, is obtainedby displacing the chain from one of the toothed wheels RD to another.

The two displacements of the chain guide 152, the primary displacement(responsible for gearshifting) and the secondary displacement(responsible for the radial distance of the chain guide from the axisZ), are thus obtained totally independently of one another, thanks tothe primary actuation means 170 and secondary actuation means 180. Itthus becomes possible to determine the optimal distance of the chainguide 152 from the axis Z in any situation, of travel or ofgearshifting.

This result has been obtained, in accordance with the second embodimentshown in FIGS. 24 to 27 and just described, by providing for thesecondary actuation means 180 to act through their motor 195 on thespring 158 of the second fixing unit.

A third embodiment of the invention is shown in FIGS. 28 to 40.

With reference to these figures, a derailleur 213 comprises a supportunit 220, configured to be mounted on the frame T of the bicycle, at theassembly of toothed wheels RD of the gearshift 1, and a mobile unit 250,comprising a chain guide 252.

The derailleur 213 also comprises primary actuation means 270 configuredto move the mobile unit 250 with respect to the support unit 220, so asto impart onto the chain guide 252 a primary displacement having atleast a component in axial direction with respect to the axis Z of theassembly of toothed wheels RD.

The derailleur 213 also comprises secondary actuation means 280configured to move the mobile unit 250 with respect to the support unit220, so as to impart onto the chain guide 252 a secondary displacementhaving at least a component in radial direction with respect to the axisZ of the assembly of toothed wheels RD. The secondary actuation means280, as will be explained hereafter, are capable of moving the mobileunit 250 independently of the primary actuation means 270.

The support unit 220 comprises a support body 221 and a first fixingunit 223, for mounting the support unit 221 on the frame T. The mobileunit 250 comprises, as well as the chain guide 252, a mobile body 251and a second fixing unit 253, for mounting the chain guide 252 on themobile body 251.

In the first fixing unit 223 a chain tensioning spring 225 is provided.

The primary actuation means 270 provide for an articulated quadrilaterallinkage between the support body 221 and the mobile body 251, which areconnected together through a pair of parallel connecting rods 271, 272,articulated both to the support body 221 at pivots 273, 274, and to themobile body 251, at pivots 275, 276.

Differently from the derailleurs 13 and 113, in the derailleur 213 thedeformation of the articulated quadrilateral linkage is obtained thanksto the connecting rod 271 being set in rotation, it being provided forthis purpose with a toothed sector 261, engaged with a motorised toothedsector 262, in the manner that will be described hereafter. The toothedsector 262 extends so as to cover for example an angle of 70°.

The deformation of the articulated quadrilateral in turn determines adisplacement of the mobile body 251 with respect to the support body 221and thus the primary displacement of the chain guide 252 with respect tothe axis Z of the assembly of toothed wheels RD.

The first fixing unit 223 comprises a pivot 226 a, intended to bemounted fixed on the frame T through a lock washer 226 b (of thedismountable type); the support body 221 and the chain tensioning spring225 are rotatably mounted on the pivot 226 a, through interposition of asliding bearing 227. The first fixing unit 223 also comprises a firstring 228, rotatably mounted on the pivot 226 a, provided with a tooth229 for resting on the frame T and with a seat 230 in engagement with afirst end of the chain tensioning spring 225.

The secondary actuation means 280 comprise a second ring 281, rotatablymounted in the support body 221 and on the pivot 226 a, 226 b andprovided with a seat 282 in engagement with a second end of the chaintensioning spring 225. The secondary actuation means 280 also comprise atoothed sector 283 formed on the second ring 281, and a toothed wheel284 (motorised in the manner that will be described hereafter) inengagement with the toothed sector 283. The toothed wheel 284 rotatesfor example by an angle of 35°-40°.

The toothed sector 262 and the toothed wheel 284 are set in rotation bya single shared electric motor 301, with a transmission 310 beingprovided for having a primary output formed by the toothed sector 262and a secondary output formed by the toothed wheel 284, respectivelyassociated with the primary actuation means 270 and with the secondaryactuation means 280. Reference numeral 301 a indicates a cable for powersupply and the control signal of the motor 301.

The chain guide 252 comprises a pair of wheels 254, 255, idle mounted onan arm 256. The second fixing unit 253 comprises a pivot 257 fixedlyconnected to the mobile body 251, on which pivot 257 the arm 256 of thechain guide 252 is rotatably mounted; a torsion spring 258 is mounted onthe pivot 257, with a first end inserted in a seat 259 formed in aninsert 263 firmly fixed in the mobile body 251 and a second end insertedin a seat 260 formed on the arm 256.

The spring 258, like the spring 225, contributes to tensioning thechain. More specifically, the two springs 225 and 258 counteract eachother: the spring 225 tends to lengthen the path of the chain angularlypushing the mobile body 251—namely, tending to rotate the mobile body251 about the pivot 226 a, 226 b in the direction M—so as to push thechain guide 252 radially away from the assembly of toothed wheels RD;the spring 258, on the other hand, tends to lengthen the path of thechain by angularly pushing the chain guide 252 in the direction N so asto push the wheel 254 radially towards the assembly of toothed wheelsRD. The setup of the chain is thus in equilibrium between the thrusts ofthese springs 225 and 258, and according to this setup the chain guide252 is more or less radially close to the axis Z of the assembly oftoothed wheels RD.

The transmission 310 comprises a casing 311 in which the motor 301 ishoused. In the casing 311 a primary shaft 312 is also rotatably housed,extending in the direction of an axis A and set in rotation by the motor301 through a reduction stage 313, which comprises toothed wheels ofdifferent diameter and of various configuration, engaged with each otherin succession, so as to determine the desired gear ratio between themotor 301 and the primary shaft 312. On the primary shaft 312 a primarytoothed wheel 314 is fixedly fitted. In the casing 311 two secondaryshafts are also housed—a first secondary shaft 315 and a secondsecondary shaft 316, parallel to one another and to the primary shaft312. A first secondary toothed wheel 317 is fixedly fitted onto thefirst secondary shaft 315, and a second secondary toothed wheel 318 isfixedly fitted onto the second secondary shaft 316.

The transmission 310 further comprises, in the casing 311, a firstoutlet shaft 320 and a second outlet shaft 321, both extending accordingto an axis B substantially perpendicular to the axis A. On the firstoutlet shaft 320, inside the casing 311, a toothed wheel 322 is fixedlyfitted (in the form of a ring provided with a toothed sector of limitedangular width) which is in meshed engagement with a worm screw 324fixedly fitted on the first secondary shaft 315. The first outlet shaft320 protrudes from the casing 311 and on it—outside of the casing311—the toothed sector 262 is fitted. On the second outlet shaft 321,inside the casing 311, a toothed wheel 323 (in the form of a ringprovided with a toothed sector of limited angular width) is fixedlyfitted, which is in meshed engagement with a worm screw 325 fixedlyfitted on the second secondary shaft 316. The second outlet shaft 321protrudes from the casing 311 and on it—outside the casing 311—thetoothed wheel 284 is fitted.

The transmission 310 further comprises, again in the casing 311, anauxiliary toothed wheel 330, mounted so as to be axially mobile in thecasing 310 along an auxiliary axis C, parallel to the axis A of theprimary and secondary shafts 312, 315, 316. The auxiliary toothed wheel330 is in meshed engagement permanently with the primary toothed wheel314 and selectively with one or other of the secondary toothed wheels317, 318. For this purpose, the auxiliary toothed wheel 330 is fixedlyfitted onto an auxiliary shaft 331, rotatably carried by a slide 332guided in a mobile manner along the auxiliary axis C, actuated for thispurpose by an electromechanical actuator 333. By acting on this actuator333, it is possible to displace the auxiliary toothed wheel 330 alongthe axis C, alternatively towards and in engagement with one or other ofthe secondary toothed wheels 317, 318 (gearshifting control condition orradial distance adjustment condition), in such a way obtaining that themotor 301 is coupled alternatively with the toothed sector 262 (throughthe reduction stage 313, the primary shaft 312, the primary toothedwheel 314, the auxiliary toothed wheel 330, the secondary toothed wheel317, the first secondary shaft 315, the worm screw 324, the toothedwheel 322, the first outlet shaft 320) or with the toothed wheel 284(through the reduction stage 313, the primary shaft 312, the primarytoothed wheel 314, the auxiliary toothed wheel 330, the secondarytoothed wheel 318, the second secondary shaft 316, the worm screw 325,the toothed wheel 323, the second outlet shaft 321).

By thus acting on the motor 301 when the actuator 333 is in thegearshifting control condition, a rotation of the toothed sector 262 isobtained and with it of the toothed sector 261, with a consequentdeformation of the articulated quadrilateral and primary displacement ofthe chain guide 252 along the axis Z.

On the other hand, by acting on the motor 301 when the actuator 333 isin the radial distance adjustment condition, a rotation of the toothedwheel 284 is obtained and with it of the toothed sector 283, of the ring281 and thus of the seat 282, thus changing the preload of the spring225 itself. Therefore, the second ring 281, the seat 282, the toothedsector 283 and the toothed wheel 284 form a linkage for adjusting thepreload of the chain tensioning spring 225, capable of determining achange in the setup of the chain guide 252 that involves the secondarydisplacement of the chain guide 252, having at least a component inradial direction with respect to the axis Z of the assembly of toothedwheels RD.

The two displacements of the chain guide 252, the primary displacement(responsible for gearshifting) and the secondary displacement(responsible for the distance of the chain guide 252 from the axis Z),are thus obtained totally independently of one another, thanks to theprimary actuation means 270 and secondary actuation means 280. It thusbecomes possible to determine the optimal radial distance of the chainguide from the axis Z in any situation, of travel or of gearshifting.

This result has been obtained, in accordance with the third embodimentshown in FIGS. 28 to 40 and just described, even in the presence of asingle motor 301, providing for the transmission 310 that places themotor 301 selectively in connection with the primary actuation means 270and with the secondary actuation means 280.

It should be noted that in this third embodiment the derailleur 213provides for the secondary actuation means 280 to act on the spring 225of the first fixing unit 223, and the casing 311 of the transmission 310to be housed on the support unit 220. In another embodiment (neithershown nor described in detail), it will be possible to use a singlemotor with an analogous transmission to the transmission 310 justdescribed, but acting on the spring of the second fixing unit; in thiscase, the casing of the transmission will be housed on the mobile unit.

The above is a description of several embodiments of inventive aspects,and further changes can be brought without departing from the scope ofthe present invention. The shape and/or size and/or position and/ororientation of the various components and/or the succession of thevarious steps can be changed. The functions of an element or step can becarried out by two or more components or steps, and vice-versa.Components shown directly connected or contacting each other may haveintermediate structures arranged between them. Steps shown as directlysubsequent can have intermediate steps carried out between them. Thedetails shown in a figure and/or described with reference to a figure orto an embodiment can apply in other figures or embodiments. Not all ofthe details shown in a figure or described in a same context neednecessarily be present in one and the same embodiment. Features oraspects that turn out to be innovative with respect to the prior art, bythemselves or in combination with other features, should be consideredas described per se, irrespective of what is explicitly described asinnovative.

For example, the primary actuation means 5 could comprise a motor actingon the diagonal of the articulated parallelogram also in the embodimentof FIGS. 28-40, and vice-versa a motor acting on one of the connectingrods also in the embodiments of FIGS. 20-23 and 24-27.

In the embodiment of FIGS. 28-40, the two outputs have the same rotationspeed, but this is not strictly necessary.

In the embodiment of FIGS. 28-40, there can be an angular positionsensor or encoder associated with the drive shaft and/or an angularposition sensor associated with the auxiliary shaft 331.

In the embodiment of FIGS. 28-40, as an alternative or in addition tothe angular position sensor associated with the drive shaft or with theauxiliary shaft 331 it is possible to provide for a pair of angularposition sensors, of which one is associated with the first outlet shaft320, and one is associated with the second outlet shaft 321.

Instead of one or more angular position sensors of the Hall effect typeit is possible to use one or more different types of sensors, such asother types of angular position sensors, sensors of the longitudinalposition of the auxiliary toothed wheel 330 in the embodiment of FIGS.28-40, angular or linear speed sensors, angular or linear accelerationsensors.

The embodiments wherein the secondary actuation means 6 act on the firstfixing unit are more advantageous with respect to the embodimentswherein the secondary actuation means 6 act on the second fixing unit inthat the transportation of signal and/or data cables to a mobilecomponent is avoided; moreover the chain guide, which is the componentthat engages with the chain and thus where maintenance is most frequent,remains freer and more accessible.

In the first and in the second embodiment, the pivots formed by thethreaded elements 26 a, 26 b and 126 a, 126 b can be replaced by pivotswith locking washer, analogous to the pivot 226 a and the washer 226 bof the third embodiment. Reciprocally, in the third embodiment, thepivot 226 a and the locking washer 226 b can be replaced by pivotsformed by two threaded elements analogous to the threaded elements 26 a,26 b and 126 a, 126 b of the first and second embodiment.

Although the invention is particularly useful in case of a rearderailleur, it can also be applied to a front derailleur.

Although the invention is particularly useful in case of a derailleurhaving an electric motor for moving the assembly of toothed wheels inthe axial direction, it can also be applied to a derailleur wherein themovement in the axial direction of the assembly of toothed wheels takesplace mechanically, for example through a Bowden cable.

In the embodiment shown in FIGS. 28-40 a conical toothed wheel 284 hasbeen used for the secondary actuation means and a cylindrical toothedsector 262 has been used for the primary actuation means. It is alsopossible to use a conical toothed wheel for the primary actuation meansand a cylindrical toothed sector for the secondary actuation means, ortwo conical toothed wheels or two cylindrical toothed sectors.

In the embodiment shown in FIGS. 28-40, a push-pull electromagneticactuator has been used, which acts on the position of the auxiliarytoothed wheel 330, displacing it between the engagement with a toothedwheel 317 part of the primary actuation means and the engagement with atoothed wheel 318 part of the secondary actuation means. It is possibleto provide for the auxiliary toothed wheel 330 to also take up anintermediate position in which it is engaged both with the toothed wheel317 part of the primary actuation means and with the toothed wheel 318part of the secondary actuation means. In this way, a mode becomesavailable in which the primary displacement and the secondarydisplacement are actuated simultaneously. Of course, in this case therest position could not be intermediate between the two toothed wheels317 and 318, so that the engaging with one of the actuation means wouldbe faster than with the other.

In the embodiment shown in FIGS. 28-40, an auxiliary toothed wheel 330has been used that is displaced in the axial direction and frontallyengages with the toothed wheel 317 and with the toothed wheel 318, thethree toothed wheels having parallel axes and the two toothed wheels 317and 318 of the primary and secondary actuation means being axiallyoffset from one another. Other embodiments can be devised, in which theauxiliary toothed wheel 330 is brought to engage with the two toothedwheels 317 and 318 with a transversal movement to the axes of thelatter; in this case it is not necessary for them to be axially offsetfrom one another.

Instead of an electromagnetic actuator, in particular of the push-pulltype, it is possible to use a different actuator to displace theauxiliary toothed wheel 330. Alternatively or in addition, any otherstructure and/or component can be used to make the transmission 310.

Instead of acting on the preload of one of the springs of the fixingassemblies, the secondary actuation means could be capable of acting onboth, acting simultaneously on both or selectively on one and/or on theother.

In the embodiments shown, the secondary actuation means always act onthe preload of a spring. However, this is not strictly necessary. As anexample, there can be a system for moving the mobile unit comprising twoelectromotors or two cascade pistons having perpendicular axes.

Indeed, it is worthwhile highlighting that through the provision of twoactuation means capable of moving the mobile unit independently in twoperpendicular directions, it is no longer necessary for the primarydisplacement of the chain guide to be oblique with respect to the axisof the assembly of toothed wheels so as to follow as much as possiblethe envelope of the toothed wheels themselves. Therefore it is also notstrictly necessary to provide for an articulated parallelogram.

What is claimed is:
 1. A method for electronically controlling a bicyclegearshift comprising a support unit configured to be mounted on abicycle frame at an assembly of toothed wheels coaxial with one anotherof the gearshift and a mobile unit comprising a chain guide, said methodcomprising the steps of: moving the mobile unit with respect to thesupport unit so as to impart onto the chain guide a primary displacementhaving at least a component in axial direction with respect to an axisof the assembly of toothed wheels; and, moving the mobile unit withrespect to the support unit so as to impart onto the chain guide asecondary displacement having at least a component in radial directionwith respect to the axis of the assembly of toothed wheels, wherein saidstep of moving the mobile unit with respect to the support unit so as toimpart onto the chain guide a secondary displacement is carried outindependently of said step of moving the mobile unit with respect to thesupport unit so as to impart onto the chain guide a primarydisplacement.
 2. The method according to claim 1, comprising, to carryout gearshifting, the steps of: a) driving a primary actuation means todisplace the mobile unit between a position of engagement of a startingtoothed wheel of the assembly of toothed wheels and a position ofengagement of a destination toothed wheel of the assembly of toothedwheels; and b) driving a secondary actuation means to displace themobile unit radially with respect to the axis of the assembly of toothedwheels.
 3. The method according to claim 2, wherein step b) comprises atleast one of the steps of: b1) driving the secondary actuation means tobring the mobile unit radially closer to the assembly of toothed wheels;and b2) driving the secondary actuation means to bring the mobile unitradially farther from the assembly of toothed wheels.
 4. The methodaccording to claim 3, wherein steps b1) where provided for, a) and b2)where provided for, are sequential to each other.
 5. The methodaccording to claim 3, wherein step b1) is at least partiallysimultaneous with step a), and step b2) is sequential to steps a) andb1).
 6. The method according to claim 3, wherein step b1) is at leastpartially simultaneous with step a), and/or step b2) is at leastpartially simultaneous with step a).
 7. The method according to claim 2,wherein step a) comprises a step of driving the primary actuation meansto displace the mobile unit between a position of engagement of astarting toothed wheel of the assembly of toothed wheels and a temporaryposition different from a position of engagement of a destinationtoothed wheel of the assembly of toothed wheels.
 8. The method accordingto claim 7, further comprising a step of staying of the mobile unit inthe temporary position for a predetermined time period.
 9. The methodaccording to claim 8, further comprising a step of driving the primaryactuation means to displace the mobile unit from the temporary positionto a position of engagement of the destination toothed wheel.
 10. Themethod according to claim 2, wherein step a) comprises driving theprimary actuation means to displace the mobile unit between a positionof engagement of a starting toothed wheel of the assembly of toothedwheels and a position of engagement of a destination toothed wheel ofthe assembly of toothed wheels not immediately adjacent to the startingtoothed wheel in the assembly of toothed wheels, directly or with astop/stops at the/each intermediate toothed wheel between the startingtoothed wheel and the destination toothed wheel.
 11. The methodaccording to claim 2, wherein step a) comprises the steps of: a1)driving the primary actuation means to displace the mobile unit betweena position engagement of the starting toothed wheel and a position ofengagement of a first toothed wheel intermediate between the startingtoothed wheel and the destination toothed wheel; a2) driving the primaryactuation means to displace the mobile unit between the position ofengagement of the first intermediate toothed wheel and the position ofengagement of the destination toothed wheel; and between said steps a1)and a2) there is at least one among the steps b11) and b21) of: b11)driving the secondary actuation means to bring the mobile unit radiallycloser to the first intermediate toothed wheel; b21) driving thesecondary actuation means to bring the mobile unit radially farther fromthe first intermediate toothed wheel.
 12. The method according to claim11, wherein step a2) comprises the steps of: a21) driving the primaryactuation means to displace the mobile unit between the position ofengagement of the first intermediate toothed wheel and a position ofengagement of a second intermediate toothed wheel of the assembly oftoothed wheels, the second intermediate toothed wheel being intermediatebetween the first intermediate toothed wheel and the destination toothedwheel; and a22) driving the primary actuation means to displace themobile unit between the position of engagement of the secondintermediate toothed wheel and the position of engagement of thedestination toothed wheel, and between said steps a21) and a22) there ispreferably at least one of the steps b12) and b22) of: b12) driving thesecondary actuation means to bring the mobile unit radially closer tothe second intermediate toothed wheel, b22) driving the secondaryactuation means to bring the mobile unit radially farther from thesecond intermediate toothed wheel.
 13. The method according to claim 2,comprising, during normal travel, the steps of: c) checking whether thecurrent position of the mobile unit with respect to the assembly oftoothed wheels corresponds to a nominal position of engagement of amotion transmission chain with a preselected toothed wheel, and in thenegative case carrying out at least one of the steps of: d) driving theprimary actuation means to displace the mobile unit between the currentposition and the nominal position of engagement; and e) driving thesecondary actuation means to displace the mobile unit between thecurrent position and the nominal position of engagement.
 14. The methodaccording to claim 13, wherein the checking step c) is carried outcyclically at a predetermined frequency and/or is carried out after apredetermined time since gearshifting from starting toothed wheel tosaid preselected toothed wheel as destination toothed wheel and/or iscarried out upon request by the cyclist.
 15. A bicycle electronicgearshift comprising at least one derailleur and a controller configuredto carry out the method according to claim 1.